/// Copyright (c) 2019 Razeware LLC
///
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to deal
/// in the Software without restriction, including without limitation the rights
/// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
/// copies of the Software, and to permit persons to whom the Software is
/// furnished to do so, subject to the following conditions:
///
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
///
/// Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
/// distribute, sublicense, create a derivative work, and/or sell copies of the
/// Software in any work that is designed, intended, or marketed for pedagogical or
/// instructional purposes related to programming, coding, application development,
/// or information technology.  Permission for such use, copying, modification,
/// merger, publication, distribution, sublicensing, creation of derivative works,
/// or sale is expressly withheld.
///
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
/// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
/// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
/// THE SOFTWARE.

import Foundation
import Accounts
import Unbox

import RealmSwift
import RxSwift
import RxRealm
import RxCocoa

class ListPeopleViewModel {

  private let bag = DisposeBag()

  let list: ListIdentifier
  let apiType: TwitterAPIProtocol.Type

  // MARK: - Input
  let account: Driver<TwitterAccount.AccountStatus>

  // MARK: - Output
  let people = BehaviorRelay<[User]?>(value: nil)

  // MARK: - Init
  init(account: Driver<TwitterAccount.AccountStatus>,
       list: ListIdentifier,
       apiType: TwitterAPIProtocol.Type = TwitterAPI.self) {

    self.account = account
    self.list = list
    self.apiType = apiType

    bindOutput()
  }

  func bindOutput() {
    //observe the current account status
    let currentAccount = account
      .filter { account in
        switch account {
        case .authorized: return true
        default: return false
        }
      }
      .map { account -> AccessToken in
        switch account {
        case .authorized(let acaccount):
          return acaccount
        default: fatalError()
        }
      }
      .distinctUntilChanged()

    //fetch list members
    currentAccount.asObservable()
      .flatMapLatest(apiType.members(of: list))
      .map { users in
        return (try? unbox(dictionaries: users, allowInvalidElements: true) as [User]) ?? []
      }
      .bind(to: people)
      .disposed(by: bag)
  }
}
